1. Field of the Invention
The present invention relates to a charged particle beam drawing apparatus and control method thereof, wherein patterns corresponding to figures included in a drawing data are drawn in a drawing area of a workpiece by applying a charged particle beam to the workpiece, wherein a resist is applied to an upper surface of the workpiece.
2. Description of Related Art
As is known in the prior art, in a charged particle beam drawing apparatus, patterns corresponding to figures included in a drawing data are drawn in a drawing area of a workpiece by applying a charged particle beam to the workpiece, wherein a resist is applied to an upper surface of the workpiece. For example, the charged particle beam drawing apparatus in the prior art is described in paragraphs 0013, 0021, 0024, 0025, and 0033 of Japanese Unexamined Patent Publication No. 2010-73918. In the charged particle beam drawing apparatus described in Japanese Unexamined Patent Publication No. 2010-73918, shot data for applying the charged particle beam is formed on the basis of the drawing data, by means of a shot forming system (shot data forming portion) (see paragraphs from 0033 to 0038 of Japanese Unexamined Patent Publication No. 2010-73918).
Also, as is known in the prior art, in a charged particle beam drawing apparatus, a parallel processing unit (PPU) is provided. For example, the charged particle beam drawing apparatus in the prior art is described in paragraphs 0022 and 0028 of Japanese Unexamined Patent Publication No. 2008-218767. And, as is known in the prior art, in a charged particle beam drawing apparatus, a writing control unit (WCU) is provided. For example, the charged particle beam drawing apparatus in the prior art is described in a paragraphs 0021 of Japanese Unexamined Patent Publication No. 2008-71929.
In a conventional charged particle beam drawing apparatus in the prior art, such as the charged particle beam drawing apparatus described in Japanese Unexamined Patent Publication Nos. 2010-73918, 2008-218767 and 2008-71929, a process, such as an Area process corresponding to a block frame, and another process, such as an Area process corresponding to another block frame, are performed in parallel by central processing units (CPUs) of the parallel processing unit (PPU). A predetermined number of central processing units (CPUs) are simultaneously used, so that a memory utilization rate of the parallel processing unit (PPU) does not exceed a predetermined value.
In one case, an actual processing load while a process corresponding to a block frame is performed, may be considerably smaller than an estimated processing load, because of diversification of the drawing data inputted to the charged particle beam drawing apparatus. In that case, in a conventional charged particle beam drawing apparatus in the prior art, only the predetermined number of central processing units (CPUs) are simultaneously used. Namely, in the conventional charged particle beam drawing apparatus in the prior art, if the actual processing load is considerably smaller than the estimated processing load, the number of central processing units (CPUs) are simultaneously used, wherein the number of central processing units (CPUs) is smaller than a number of usable central processing units (CPUs). Consequently, in the conventional charged particle beam drawing apparatus in the prior art, if the actual processing load is considerably smaller than the estimated processing load, throughput cannot be sufficiently increased.
In another case, an actual processing load may be considerably larger than an estimated processing load, while a process corresponding to a block frame is performed, because of diversification of the drawing data inputted to the charged particle beam drawing apparatus and miniaturization of figures included in the drawing data. In that case, in a conventional charged particle beam drawing apparatus in the prior art, the predetermined number of central processing units (CPUs) are simultaneously used. Namely, in the conventional charged particle beam drawing apparatus in the prior art, if the actual processing load is considerably larger than the estimated processing load, the memory utilization rate of the parallel processing unit (PPU) may exceed a limit value. In the conventional charged particle beam drawing apparatus in the prior art, if the memory utilization rate of the parallel processing unit (PPU) exceeds the limit value, a process of the parallel processing unit (PPU) is performed by using a storage device, wherein processing speed and accessing speed of the storage device is slower than processing speed and accessing speed of a memory of the parallel processing unit (PPU), accordingly, throughput may be considerably decreased.